Biology & Philosophy

, 33:42 | Cite as

Moral talk and indirect reciprocity: direct observation enables the evolution of ‘moral signals’

  • Connor Robinson-ArnullEmail author


A prominent explanation of the evolution of altruism is ‘indirect reciprocity’ where the tracking of reputations in a population promotes altruistic outcomes. This paper investigates the conditions under which the meaning of reputation-tracking signals can co-evolve with altruistic behaviours. Previous work on this question suggests that such a co-evolution is unlikely. In our model, we introduce a mixture of direct and indirect information: individuals directly observe the actions and signals of others with some probability, rather than individuals always relying only upon information conveyed through signals. In this context, we see the co-evolution of altruism and the kind of ‘moral signals’ required for individuals to track reputation. Our interpretation of this model is that, although individuals can sometimes observe the behaviour of their fellows directly, they cannot always do so, and signals evolve to fill this gap. Although ‘can’ does not imply ‘must’—that our model can produce this co-evolution does not establish that we have found the only possible mechanism—we nonetheless consider this an interesting possibility result worthy of further investigation.


Altruism Indirect reciprocity Partner choice Moral norms Moral signals Reputation 


  1. Cavalli-Sforza LL, Menozzi P, Piazza P (1996) The history and geography of human genes. Princeton University Press, PrincetonGoogle Scholar
  2. Ghang W, Nowak MA (2015) Indirect reciprocity with optional interactions. J Theor Biol 365:1–11CrossRefGoogle Scholar
  3. Leimar O, Hammerstein P (2001) Evolution of cooperation through indirect reciprocity. Proc R Soc Lond Ser B 268:745–753CrossRefGoogle Scholar
  4. Nowak MA, Sigmund K (1998) Evolution of indirect reciprocity by image scoring. Nature 393:573–577CrossRefGoogle Scholar
  5. Nowak MA, Sigmund K (2005) Evolution of indirect reciprocity. Nature 437:1291–1297CrossRefGoogle Scholar
  6. Roberts G (2015) Partner choice drives the evolution of cooperation via indirect reciprocity. PLoS ONE 10(6):1–11Google Scholar
  7. Smead R (2010) Indirect reciprocity and the evolution of “moral signals”. Biol Philos 25(1):33–51CrossRefGoogle Scholar
  8. Tanaka H, Ohtsuki H, Ohtsubo Y (2016) The price of being seen to be just: an intention signalling strategy for indirect reciprocity. Proc R Soc Lond B 283:20160694CrossRefGoogle Scholar
  9. Trivers RL (1971) The evolution of reciprocal altruism. Q Rev Biol 46:35–57CrossRefGoogle Scholar
  10. Weibull JW (1995) Evolutionary game theory. MIT Press, CambridgeGoogle Scholar

Copyright information

© Springer Nature B.V. 2018

Authors and Affiliations

  1. 1.Philosophy DepartmentCarnegie-Mellon UniversityPittsburghUSA

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